# Package net.sf.saxon.event

This package provides classes that feed SAX-like events from one tree to another.

See: Description

- Interface Summary
  Interface | Description
  --- | ---
  CopyInformee | A CopyInformee is an agent that receives extra information while a tree is being copied.
  FilterFactory | Factory class to create a ProxyReceiver which filters events on a push pipeline
  LocationProvider | LocationProvider: this interface represents an object that provides the location of elements in a source document or instructions in a stylesheet or query.
  Receiver | Receiver: This interface represents a recipient of XML tree-walking (push) events.
  SaxonLocator | SaxonLocator: this interface exists to unify the SAX Locator and JAXP SourceLocator interfaces, which are identical.
  SourceLocationProvider | A SourceLocationProvider is a `LocationProvider` that represents locations in the source document from which the events are derived (as distinct from locations in a query or stylesheet of the instructions causing the events)

- Class Summary
  Class | Description
  --- | ---
  Builder | The abstract Builder class is responsible for taking a stream of SAX events and constructing a Document tree.
  BuilderMonitor | A BuilderMonitor can be inserted into a pipeline immediately in front of a Builder.
  CommentStripper | The CommentStripper class is a filter that removes all comments and processing instructions.
  ComplexContentOutputter | This class is used for generating complex content, that is, the content of an element or document node.
  ContentHandlerProxy | A ContentHandlerProxy is a Receiver that converts events into the form expected by an underlying SAX2 ContentHandler.
  ContentHandlerProxy.ContentHandlerProxyTraceListener | Create a TraceListener that will collect information about the current location in the source document.
  ContentHandlerProxyLocator | Implementation of Locator, used to supply location information to the ContentHandler.
  EventSource | An implementation of the JAXP Source class that supplies a document in the form of a stream of push events sent to a Receiver
  IDFilter | IDFilter is a ProxyReceiver that extracts the subtree of a document rooted at the element with a given ID value.
  LocationCopier | A Receiver that can be inserted into an event pipeline to copy location information.
  NamePoolConverter | This class is a filter that passes all Receiver events through unchanged, except that it changes namecodes to allow for the source and the destination using different NamePools.
  NamespaceReducer | NamespaceReducer is a ProxyReceiver responsible for removing duplicate namespace declarations.
  OnEmptyHandler | This receiver is inserted into the output pipeline whenever on-empty is used (XSLT 3.0) on a literal result element, on xsl:element, or on xsl:copy when processing elements.
  PathMaintainer | This class sits in a receiver (push) pipeline and maintains the current path.
  PIGrabber | The PIGrabber class is a Receiver that looks for xml-stylesheet processing instructions and tests whether they match specified criteria; for those that do, it creates an InputSource object referring to the relevant stylesheet
  PipelineConfiguration | A PipelineConfiguration sets options that apply to all the operations in a pipeline.
  ProxyReceiver | A ProxyReceiver is an Receiver that filters data before passing it to another underlying Receiver.
  ReceiverOptions | ReceiverOptions defines a set of constants, which can be used in calls to methods on the Receiver interface.
  ReceivingContentHandler | ReceivingContentHandler is a glue class that provides a standard SAX ContentHandler interface to a Saxon Receiver.
  Sender | Sender is a helper class that sends events to a Receiver from any kind of Source object
  SequenceCopier | Copies a sequence, supplied as a SequenceIterator, to a push pipeline, represented by a SequenceReceiver
  SequenceOutputter | This outputter is used when writing a sequence of atomic values and nodes, that is, when xsl:variable is used with content and an "as" attribute.
  SequenceReceiver | SequenceReceiver: this extension of the Receiver interface is used when processing a sequence constructor.
  SequenceWriter | This outputter is used when writing a sequence of atomic values and nodes, for example, when xsl:variable is used with content and an "as" attribute.
  Sink | A Sink is an Receiver that discards all information passed to it
  StartTagBuffer | StartTagBuffer is a ProxyReceiver that buffers attributes and namespace events within a start tag.
  StreamWriterToReceiver | This class implements the XmlStreamWriter interface, translating the events into Saxon Receiver events.
  Stripper | The RuleBasedStripper class performs whitespace stripping according to the rules of the xsl:strip-space and xsl:preserve-space instructions.
  Stripper.StripRuleTarget |
  TeeOutputter | TeeOutputter: a SequenceReceiver that duplicates received events to two different destinations
  TracingFilter | A filter that can be inserted into a Receiver pipeline to trace the events that pass through.
  TransformerReceiver | TransformerReceiver is similar in concept to the JAXP TransformerHandler, except that it implements Saxon's Receiver interface rather than the standard SAX2 interface.
  Transmitter | A Transmitter is a source of events sent to a Receiver.
  TreeReceiver | A TreeReceiver acts as a bridge between a SequenceReceiver, which can receive events for constructing any kind of sequence, and an ordinary Receiver, which only handles events relating to the building of trees.
  TypeCheckingFilter | A filter on the push pipeline that performs type checking, both of the item type and the cardinality.

- Exception Summary
  Exception | Description
  --- | ---
  CopyNamespaceSensitiveException | Exception indicating that an attempt was made to copy namespace-sensitive content without copying its associated namespaces
  NoOpenStartTagException | Exception indicating that an attribute or namespace node has been written when there is no open element to write it to

## Package net.sf.saxon.event Description

This package provides classes that feed SAX-like events from one tree to another. Some of these classes are associated with serializing the output of a stylesheet, but there are also classes for building a tree from a stream of events, for stripping whitespace, and so on.

The `Receiver` interface defines a class that accepts a stream of events, with one method defined for each kind of event. The events are modelled on the design of SAX, but adapted to the XPath data model and to the use of Saxon's NamePool. Attributes and namespaces are notified individually after the start of the relevant element. Many of the classes in this package are implementations of the `Receiver` interface.

The immediate output of node constructors in a query or stylesheet goes to a `SequenceReceiver`. This is a subclass of `Receiver` that can handle an arbitrary sequence, containing atomic values as well as nodes. When constructing the content of an element, a `ComplexContentOutputter` is used; when constructing the content of a node such as a text node or attribute, a `SequenceOutputter` is used instead.

The final destination of the push pipeline is sometimes a serializer, and sometimes a tree builder. The final serialization classes are subclasses of `Emitter`, but some of the serialization work (such as indentation or application of character maps) is done by other classes on the pipeline. These are generally constructed by extending the `ProxyReceiver` class.

The Emitter is an abstract implementation of the Receiver interface. As well as supporting the Receiver interface, it provides methods for controlling the destination of serialized output (a Writer or OutputStream) and for setting serialization properties (in a Properties object). In practice nearly all the implementations of Receiver are currently subclasses of Emitter, but this may change in the future.

The package includes emitters for the standard output methods xml, html, and text, and proxy emitters to allow a sequence of filters to be applied to the output.

,

The class `ContentHandlerProxy` allows events to be converted into standard SAX events and sent to a SAX2 `ContentHandler`. Similarly, the class `ProxyReceiver` acts as a `ContentHandler`, accepting SAX2 events and feeding them into a `Receiver` pipeline.

The class `Builder` is a `Receiver` that constructs a tree representation of the document in memory. There are two subclasses for Saxon's two native tree models. Other classes such as a `Stripper` and a `NamespaceReducer` are used to modify the document by adding filters to the pipeline.

Saxon's schema validator and serializer are both implemented using this push pipeline model. The classes that perform schema validation are part of package: `com.saxonica.validate`, while the serialization classes are in `net.sf.saxon.serialize`.

Michael H. Kay
Saxonica Limited
30 July 2010

Copyright (c) 2004-2013 Saxonica Limited. All rights reserved.